The conventional techniques for treating knitted fabrics in tubular form prior to cutting and sewing the fabrics into garments provides fabrics having residual shrinkage in the range of 25%. When the fabric is formed into garments and sold to the public, the fabric is normally oversized to some degree and as the garment is subjected to normal wear and washing, it shrinks. A tubular knit fabric is designed to stretch to conform to the body of the wearer, and the fact of cotton fabric shrinkage has been an accepted characteristic which the public must tolerate when seeking the advantage of cotton knit fabrics.
To control shrinkage, resins are applied to the fabric either during the fabric finishing operation or during the yarn preparation phase of the operation. Such treatment is expensive and eventually adversely affects the longevity of the fabric and detracts from the soft "hand" of the fabric. Furthermore, most resins contain formaldehyde which is deemed unsafe at certain levels in the workplace and on the product.
During the preparation of the knitting yarn and during the knitting operation, lubricants and waxes are used and other foreign matter may become entrapped in the fabrics which preferably should be removed before the fabric is made into garments. Commonly the fabric is separated into batches which are washed and dried individually in tumble washers and dryers. The handling of the batches of fabric while wet tends to impart stresses and strains to the fabric tubes, which strains may or may not be relieved during subsequent processing operations, and the resulting fabrics are characterized by shrinkage which is not uniform and which may vary in residual shrinkage from as low as 10% to as high as 25%.
In the case of thermal knit fabrics, the fabric is characterized by air-entrapping cells or pockets on one or both sides which provide dead air spaces in the fabric. These cells are produced by the knit construction during knitting of the fabric and are disposed in longitudinal and transverse rows. Known as "waffle knit" fabric, the development of thermal knit fabric since 1951 is briefly described in U.S. Pat. No. 4,678,693, the disclosure of which is incorporated herein by reference.
In a common type of thermal fabric, the knit construction provides in the neighborhood of 5.25 cells per inch in both the lengthwise and transverse direction and a typical density in the range of 51/2 ounces per square yard. To counteract the effect of the residual shrinkage, the fabric has typically been subjected to compaction and setting with formaldehyde resin treatment.
In efforts to obtain more uniformity, the batch treatment has been replaced by continuous treatment, but it has been found that the conventional continuous treatment has resulted in residual shrinkage in the range of 25%. Attempts to reduce the shrinkage without chemical treatment of the fabric have previously been directed to the final stages of the finishing operations, specifically during the drying operation following the washing and scouring and other chemical treatment of the fabric after it comes from the knitting machines. Although such treatments reduce the residual shrinkage to some degree, none has proved entirely satisfactory.